Another big factor is camera size/viewfinder position. If you're shooting a medium format camera with the standard waist level finder, you tripod can be a foot and a half shorter than if you're shooting a 35mm SLR. If you're using a view camera, you'll probably need to be able to see the entire rear of the camera, from every angle, including from above the top corners.
Personally, I can't stand a tripod that's even a little too short. If I can't stand behind it comfortably, then I'm not likely to use it. Which means I'll end up handholding anyway. So for me, a tripod that was 6 inches too short would be comepletely useless.